Primordial Assumptions and Non-Falsifiable Objections

Greetings,

It is common to make several assumptions when discussing philosophical matters-- whether one's interest is ontological, epistemological, formally logical, or some other field, primordial assumptions are a key underlying element. These assumptions are fundamental to our experience of the world, and thus tend not to be challenged further unless they are the specific matter of inquiry, because to do so would drastically shift the inquiry and possibly send a skeptic down a "rabbit hole" (as I call them) where an unceasing flurry of questions, each causing another question, that result in a completely unproductive endeavor with all participants exhausted and discouraged. Examples I have seen fellow discussants perform in conversations include challenging the law of noncontradiction, denying the legitimacy of free will, and proposing that everything "is a dream" while discussing other topics. It is, of course, completely legitimate to discuss these issues when they are the focus or topic of conversation. However, when one discusses an argument for the existence of God or the nature of animal ethics, challenging a core assumption by claiming that everything is just a dream seems both counterproductive and, perhaps, ad hoc, as the claims tend not to be considered legitimate outside of the specific conversation. I would pay money to see what would happen if you commit perjury by stating that you didn't see a crime, and later deny that you committed perjury by asserting that the law of noncontradiction is illegitimate.

On the other hand, we want our arguments to be falsifiable, and thus to be able to deal with objections. If I argue that humans do not have ethical obligations to animals because animals do not have free will, but I imply that humans do have ethical obligations to each other (because they have free will), it seems relevant to bring the question of fatalism into the picture. And yet, here we seem to have a quandary: if free will does not exist, we cannot concede the argument as being valid or invalid on the basis of the validity of the argument (rather, one was compelled to evaluate the argument in the matter one evaluated it, regardless of the ontological validity of the argument). As such, we lose our capacity to evaluate the argument. It would seem that the individual who challenges free will thus cannot meet the standard of falsifiability-- their argument cannot be falsified if there is no free will, because there is no one to falsify it. However, the fatalism objection seems both coherent and relevant. A topic can become controversial when it is not falsifiable; how much more difficult a topic becomes when one of its most coherent objections is not falsifiable!

What tactic should we take when we a legitimate topic has a non-falsifiable objection thrust at it? Do we deny the legitimacy of the objection, or treat it with all seriousness? Do we disregard it as sophistry, or do we attempt to account for it? It's a topic of both practical and theoretical interest to me, and I look forward to your feedback.

EDIT: On a completely unrelated note, here's a rather disturbing document you should probably see, about one of our favorite meeting locations...
http://ga.state.gegov.com/_templates/87/Food/_report_full.cfm?fsimID=1441174&domainID=87&rtype=food